Descriptions

PDMS membrane-based microvalves are becoming increasingly more important for the control of fluid flow within MECS applications such as microreactors used to synthesize nanoparticles and biological macromolecules. The motivation for pursuing PDMS membrane-based microvalves is for implementing a plug flow microreactor to simulate slug flow yielding a narrower residence time distribution (RTD). Barriers to the use of PDMS membrane-based microvalves within these types of MECS applications include the need to be scalable and compact, capable of operating at higher pressures in a variety of solvents. Most current bonding architectures for PDMS membrane-based microvalves are limited to one atmosphere.
This research work describes the design, analysis, fabrication, and characterization of PDMS membrane-based microvalve architecture for implementation within MECS devices for nanoparticles synthesis applications. The new fabrication approach is to make reliable bonds capable of withstanding higher pressures. The approach developed in this thesis eliminates bonding constraints within current PDMS bonding architectures (e.g. bonding of dissimilar materials and stress distribution problems) through the use of sealing bosses and enables further miniaturization of the overall structure by entrapping the membrane between stiff polymer substrates.
A novel fabrication method has been developed for embedding PDMS membrane-based microvalves in multi-layer, arrayed microfluidic devices. This novel architecture sandwiches an elastomeric membrane between polycarbonate substrates having sealing bosses and can withstand operating pressure upto 100 psi. This meets a key requirement for MECS device architectures which require higher fluidic pressures in a chemical processing. In addition, the architecture incorporates the use of stiff polymers which can reduce the overall size of the device. Based on the fact that a polycarbonate lamina has an elastic modulus 1000 times that of a PDMS lamina (currently used in multi-layer valve architectures), plate mechanics would predict a 10 fold reduction in the thickness of those laminae to achieve the same stiffness within the stack.